Ships for shallow waters have little draught and, therefore, react sensitively to weight and displacement changes, in particular for the passage of water through the propulsion device, channels or tunnels are provided in the ship's hull. Moreover, such ships are much endangered due to striking underwater objects and should moreover be very maneuverable.
A propulsion device for such watercrafts should, therefore, at the same time meet the following tasks. The propulsion device must be recessed in a protected manner, in particular protecting same against engagement with underwater objects and it must be suited for small maneuverable vehicles because of the narrow waterways through which it often must move. Thus the propulsion device must require a small amount of space and be of a light weight. Because of the shallow waters which must be travelled, the propulsion device must function self-drawingly at a very small draught and must be insensitive to small water depths and bottom clearances of the ship, in particular insensitive against the flowing through of sand, stones, ice and other contaminants. The requested good maneuverability is best solved with a smooth round controllable thrust jet.
Hydro-jet propulsion devices are already known, which, however, do not meet in combination the above-listed conditions. In particular they do not meet the requirement for a small enclosed area, small weight and good efficiency in an optimum manner.
Therefore, an object of the invention is to provide a hydro-jet propulsion device of the above-described type having a light weight, small space requirement and good efficiency.
The basic object of the invention is met with a hydro-jet propulsion device wherein the axis of rotation of the impeller of the pump is oriented eccentrically with respect to the axis of rotation of the elbow.
The pump is thereby a propeller or radial pump of an axial, semi-axial or radial construction.
An elbow is a device which diverts a jet of water from one direction into another direction, thus for example includes also a spiral housing which diverts a jet of water which is axial with respect to the pump into a radial jet.
The efficiency of the jet propulsion is increased by a development of the invention wherein the axis of rotation of the impeller is inclined to the vertical. This embodiment has also the advantage, that the reaction moment of the pump acts less on the control drive.
Further advantages and characteristics of the invention can be taken from the following description.